Heterotopic Transplantations Reveal Environmental Influences on Interneuron Diversity and Maturation

During embryogenesis, neural progenitors in the ganglionic eminences give rise to diverse GABAergic interneuron subtypes that populate all forebrain regions. The extent to which these cells are genetically predefined or determined by postmigratory environmental cues remains unknown. To address this question, we performed homo- and heterotopic transplantation of early postnatal MGE-derived cortical and hippocampal interneurons. Grafted cells migrated, and displayed neurochemical, electrophysiological, morphological, and neurochemical profiles similar to endogenous interneurons. Our results indicate that the host environment regulates the proportion of interneuron classes in the brain region. However, some specific interneuron subtypes retain characteristics representative of their donor brain regions. GABAergic interneurons are an extremely heterogeneous cell population, but the mechanisms directing this diversity remain unclear. Quattrocolo et al. challenged interneuron precursors in new environments via heterotopic transplantations in order to investigate how the environment influences interneuron diversity.